As the temporal quality is decreased, the bandwidth of the sequence will decrease also. However, decreasing the temporal quality increases the number of artifacts (blocks and/or streaks) in the image.
In your case, adding temporal compression is apparently increasing the noise level. The noise you're experiencing is probably the result of pixel level values that change rapidly over time, causing a 'living' background of various pixels that are constantly changing values. This could be due to tape quality, but if you are converting from a pure digital resource to QuickTime, tape quality issues are eliminated.
Make sure that the contrast levels are calibrated, so that black is black, and white is white. The more pixels you have with the same contrast level, the more CinePak will adjust the values to similar or near-similar pixel values, which could cause additional noise.
Noise can also be generated by the background of the video image. For example, a constantly changing background, such as trees or grass moving in the wind, can cause noise due to the constantly changing pixels in the background. The CinePak codec tries to adjust these constantly changing values to something near average, causing pixel flashes.
Adding key frames to reduce the temporal values between the key frames should result in better quality images. As you increase the size of the movie, you also increase the bandwidth needed to load the movie.
You can use a combination of these techniques to deal with the noise, but as
you can probably tell, this is a tuning process, so the results you get will
vary with the original images, making it difficult to predict your results in
all cases.
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